Hi Andreas,
I think I know what the cause of this might be. The problem is that the DropSync browser view only shows you folders that actually exist on your hard drive ... but ... it looks like at some stage in the past you selected a folder called /Users/myname/Documents/work/!Privat/./Outlook ... and DropSync is still trying to sync this even though it no longer exists.
The solution is to switch to the "list" view ... and you should be able to see the offending folder and remove it from the list of items to sync. You can switch to the list view using the View button in the toolbar.
I hope that helps
Ira